Method for vacuum melting and casting



Aug. 12, 1969 s, T ET AL 7 METHOD FOR VACUUM MELTING AND CASTING 6 Sheets-Sheet 1 Original Filed Dec.

FIG. 1

VACUUM IN VENT ORS STANLEY C. TINGQUIST ALBERT M. TALBOT WILLIAM H. HAGEDORN I v ATTQRNEYS 6 Sheets-Sheet 2 Aug. 12, 1969 s. c. TING QUIST E L METHOD FOR VACUUM MELTING AND CASTING Original Filed Dec. 16, 1964 FIG. 2

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METHOD FOR VACUUM MELTING AND CASTING Original Filed Dec. 16, 1964 FIG. 3

a sheets she et s I STANLEY C.TINGQUIST ALBERT M. TALBOT BY WILLIAM H. HAGEDORN K m Em,

ATTORNEYS Aug. 12, 1969 5, c, T'INGQUIST ET AL 3,460,304

METHOD FOR VACUUM MEL'IING AND CASTING Original Filed Dec. 16, 1964 6 Sheets-Sheet 1 N. If I 6 r I IQVQ /v m L: 9 v64 4 7 8 8 m 1 a Ill \\H\ MD n- Hwu1iLni m 8 I w 3 w O O o A 0 N A I r F vi H L Q 8 O 6 O7 5 M F 4 ay I, ll A m (11%; fish ATTORNEY S s. c. TINGQUIST ET AL 3,460,604 METHOD FOR VACUUM MELTING AND CASTING Original Filed Dec. '16; 1964 Aug. 12, 1969 6 Sheets-Sheet 5 INVENTORS STANLEY c. TINGQUIST ALBERT M. TALBOT WILLIAM H. HAGEDORN A W", w-s ATTORNEYS Aug. 12, 1969 s. c. TINGQUIST ET 3,460,604

METHOD FOR VACUUM MEL'IING AN!) CASTING Original Filed Dec. 16, 1964 6 Sheets-Sheet 6 GEDOR I 4 ATTORNEYS 3 IN VENTORS STANU-IY C. TINGQU IST ALBERT M. TALBOT LLlAzll H United States Patent 3,469,604 METHOD FOR VACUUM MELTIN G AND CASTIN Stanley C. Tingquist, Sparta, Albert M. Talbot, Mountain Lakes, and William H. Hagedorn, Mount Arlington, N.J., assignors to Howmet Corporation, a corporation of Deiaware Original application Dec. 16, 1964, Ser. No. 418,770, now Patent No. 3,336,971, dated Aug. 22, 1967. Divided and this application Mar. 24, 1967, Ser. No. 641,715

Int. Cl. B22d 27/16, 17/02 US. Cl. 164-61 4 Claims ABSTRACT OF THE DISCLOSURE A method for vacuum melting and casting in which a continuous vacuum is maintained in the vacuum meltlng and casting zones by first loading a metal charge into a loading zone, creating a vacuum in the loading zone and then opening the loading zone to a melting zone and thereafter continuously maintaining the melted charge under a vacuum until it is cast.

CROSS-REFERENCE TO RELATED APPLICATIONS This is a divisional of copending application, Ser. No. 418,770, filed Dec. 16, 1964, now Patent No. 3,336,971, issued Aug. 22, 1967.

This invention relates to vacuum melting and casting of metals. More particularly it relates to a continuous method of melting and casting metals under a constant vacuum.

Metals and metallic compounds are processed within a vacuum to prevent atmospheric oxidation, to allow deoxidation with carbon in the melt and to remove other dissolved gases such as hydrogen and nitrogen. Casting under the vacuum further reduces atmospheric contamination. It is therefore desirable to provide apparatus which will permit the vacuum melting and casting zone to be maintained under a continuous vacuum throughout the operation of the apparatus. If the vacuum is preserved in the melting and casting zone throughout the operation of the apparatus, the quality of the castings can be greatly improved. For this reason all the present commercial continuous vacuum furnaces have a locker chamber for loading the molds and a separate locker system for charging the alloy, the purpose being to pro vide means for loading the molds and charging the alloy which are separate from the furnace chamber so as to preclude, as much as possible, contamination within the furnace chamber while still permitting relatively continuous operation.

The invention provides a new method of vacuum casting which consists of loading a metal charge in a loading zone and creating a vacuum in this loading zone. The loading zone is then opened to a melting zone which is continuously maintained under a vacuum. The metal charge is then fed into the melting zone and is heated to molten metal in the melting zone. The molten metal is then cast in the melting zone and the cast metal and mold are then removed from the melting zone to the loading zone. The loading and melting zones are closed off from each other and then the cast is removed from the loading zone.

A preferred embodiment of the invention is described hereinbelow with reference to the drawings wherein:

FIG. 1 is a plan view partly in section showing the apparatus of the invention;

FIG. 2 is a side elevation taken along the lines 2-2 of FIG. 1;

FIG. 3 is a fragmentary side elevation of the charge feed and mold positioning means of the apparatus;

ice

FIG. 4 is a section of a portion of the charge feed taken substantially along lines 44 of FIG. 3 with the ingot inserted in the crucible;

FIG. 5 is a side elevation taken along one side of the melt chamber showing the means for rotating the crucible and indicating a method of connecting it to a power source and making alloy additions to the crucible;

FIG. 6 is a section taken along lines 6-6 of FIG. 5; FIG. 7 is a section taken along lines 7- 7 of FIG. 1; and

FIG. 8 is a section taken along lines 8-8 of FIG. 1.

FIGS. 1, 2 and 5 show two closed chambers-a single load chamber 10 and a furnace chamber 11. These chambers in their operating condition are both characterized by being substantially airtight so that a high vacuum can be maintained therein. The load chamber is comprised of top closure 12, bottom plate 13 and side wall plates 14 and is not completely closed until it is in its operating position adjoining the furnace chamber 11. This is due to the construction of the load chamber wherein it is open on two adjoining sides. One side 15, which faces outwardly from the joined chambers in their operating positions, has an outer opening 16 therein which can be closed by outer door 17. The outer door is hinged to the chamber and contacts the chamber flush against the side 15 of the chamber. A peripheral gasket 18 is positioned about the opening 16 and a latch 19 is mounted on the door 17 to lock the door in flush contact against the side 16 of the chamber tightly against the gasket 18 when the chamber is closed to the outside.

On side 20 adjoining the side 16, there is another large opening 21 which is in alignment with an opening 22 in side 23 of the furnace chamber 11. This side 23 of the furnace chamber 11 has a gasket 24 mounted therein which is positioned about the periphery of the opening to contact the adjoining side 20 of the load chambers when the load and furnace chambers are locked together.

Mounted on the load chamber 10 at the opening 21 is a bulkhead door 25. This door 25 is hung on a shaft 26 which is rotatably mounted in the bottom plate 13 and the top plate 12 of the load chamber 10, with the top end 27 of the shaft extending beyond the top plate, and is supported in this position by vertically spaced hinge joint and bearing assemblies 28 mounted on the inner side walls of the chamber. A pair of binge bars 29 are attached to the shaft 26 and extend laterally from it and are attached to the door 25 by the screws extending therethrough as shown in FIG. 8. The hinge bars are maintained spaced apart and supported by a diagonally extending fiat bar 30 welded thereto which is folded about the lower hinge bar and is also attached to the upper hinge bar by a bolt 31 which extends through a bar 310, which is welded to the door, and through the upper hinge bar.

Attached to the top end 27 of the shaft 26 and extending beyond the chamber is a connecting rod 32 which has its opposite end 33 connected to clevis 34. The clevis- 34 is mounted on the plunger of a. hydraulic cylinder 35 which is mounted at the top of the load chamber for turning the shaft and opening and closing the bulkhead door.

In its closed position, the bulkhead door 25 is designed to close the opening 21 so tightly that the desired high vacuum can be maintained in the furnace chamber and will not be affected by any appreciable leakage through the door. The door is also cooled to prevent heat warpage and to maintain its flatness for good sealing. As will be seen, the furnace chamber is essentially a cold-walled furnace that is water-cooled so as to maintain the furnace near ambient temperature during high temperature operations. A gasket 36 is mounted in grooves in the marginal edge portions of the door along the surface thereof which faces toward the furnace chamber in the closed position. The spacing of the gasket 36 is such that it is wider in all dimensions than the opening 21; thus when the door is closed flush against the side 23 of the furnace chamber 11 in which the opening 21 is defined, the gasket is in flush contact with the side 23 to preserve the substantially airtight seal therebetween.

In order to prolong the life of the gasket 36 and to control the heat on the door 25, a cooling system consisting of copper tubing 37 is mounted in a pattern along the side of bulkhead door which faces toward the first chamber in the closed position and this tubing is connected to a water source for circulation of water therethrough. The pattern is such that the copper tubing is mounted directly behind the gasket as much as possible, but it crosses back and forth across the width of door several times; thus the gasket life is prolonged by positioning of the tubing and the entire door surface is maintained cooler by the presence of the tubing. The water is fed into the load chamber 10 through an inlet fitting 38 which is interconnected to the tubing mounted on the door by a flexible hose coniection 39. An outlet fitting 40 also extends through a wall of the load chamber and is similarly connected to the opposite end of the tubing by a flexible hose connection 41. The flexible connections permit the door to be opened and closed.

Mounted on the side of the door which faces into the furnace chamber in the closed position is a radiation heat shield 42. This heat shield in this embodiment is a mesh 3f stainless steel wire and is supported on the door in spaced relationship thereto by a bolt and collar assembly 43. The purpose of the heat shield is to retard radiation 3f heat on the door which might distort the door and the gasket causing a poor seal between the chambers,

Positioned beneath substantially the four corners of .he load chamber 10 are four pairs of wheels 44 which Jermit the load chamber to be rolled into contact and alignment with the furnace chamber. This case of physical leparation of the load chamber provides access to the furnace chamber for cleaning and maintenance purposes.

It is to be noted that an outer edge portion of the side 53 of the furnace chamber on which a portion of the gasket 24 is mounted is defined by a flange plate 45 which extends laterally outwardly from the opening 22 1nd defines the flat surface for abutment with the load :hamber side wall 20. By rolling the load chamber into alignment with the stationary furnace chamber, the respecive chambers can be connected for operation. The chamaers are maintained in their operating position, with the adjoining side walls and respective gaskets in flush abutnent by two pairs of latches, one pair 46 and 47 of which tre shown in FIG. as mounted on the side wall 20 of the oading chamber. Of course a similar cooperating pair are also mounted on the side wall of the loading chamber n he opposite side of the furnace chamber. In the operaional position the latches 46 and 47 are positioned adacent one side edge of the flange plate 45 and locks about he flange portion, as does the pair of latches on the oppo- :ite side, to hold the respective chambers tightly together.

Refering now particularly to FIGS. 1, 2 and 5, with the 'urnace chamber 11 which is the melt chamber of the ap- Jaratus is shown. Extending integrally from the flange late 45 of the furnace chamber is a substantially U-shaped ody 50 which is formed of spaced double-walled plates 51 and 52 which are spaced to define a water jacket therenetween. The furnace chamber 11 is also preferably closed ll. the top and bottom thereof by double-walled to plates 5 and bottom plates 56. As shown a water jacket 57 is lefined between the double-walled top plates and side wall mlates, and a similar construction can advantageously be 156d in the bottom plates. By providing the water jacket hrough substantially the entire housing of the furnace :hamber with the exception of those portions which will e described below through which various elements are in- .erted through the housing wall, a coolant such as water 4. may be circulated through the wall of the housing of the furnace chamber to prevent the exterior of the housing from becoming excessively hot and to provide a cold wall furnace. The furnace chamber is supported on vertical supports 58 and 59 to maintain it spaced from the floor. Extending through a portion of the top plates and the side walls 50 is a relatively large diameter vacuum exhaust 60 which in turn is connected to a suitable vacuum pumping means to maintain the desired high vacuum within the furnace chamber. As shown a similarsmaller diameter vacuum exhaust 61 opens into the load chamber and is also connected to a vacuum pump means for evacuating the load chamber during one stage of the operation to preserve the continuous vacuum in a manner to be described below. In this embodiment, the pumping system involved a 20-inch oil diffusion pump backed by a 300 c.f.m. mechanical pump on the furnace chamber and a 1200 c.f.m. blower backed with a 130 c.f.m. mechanical pump on the load chamber. The apparatus is designed for casting of high purity metals and the pressure will fall within the high-vacuum region, below 1 mm. Hg and usually around 10- mm. Hg for vacuum casting.

It is in the furnace chamber in which a metal ingot is to be melted under a high vacuum to molten metal and then poured into the desired mold to cast the metal in the intended shape. In order to effect this melting of the ingot, a crucible 63 is positioned within the furnace chamber. This crucible is generally lined with a suitable refractory material and any of the known electric crucibles suflicient to heat the ingot to a melting temperature which generally use arc, induction coils or resistance windings located in the crucible can be used. The substantially cylindrical crucible 63 is mounted between a pair of spaced parallel plates 64 and 65 by means of radially extending supporting members 66. Extending laterally from the spaced parallel plates 64 and 65 are trunnions 67 and 68. The trunnions are journalled in bearings 69 and 70 which bearings are supported on plate and bracket assemblies 71 and 72 and are secured to the inner side walls of the chamber. Positioned within the plate and bracket assemblies 71 and 72 between the plate and bracket is an electrically insulating shield 73, which serves to break the electric field. It is to be noted that the trunnions extend from the respective plates at a position out of alignment with the center of the crucible and in this embodiment .are connected to the plates along a portion thereof which extend-s outwardly beyond the pouring side of the crucible. Thus when the crucible is pivoted on its axis defined by the trunnions to effect tilt- 1ng suflicient to pour the molten metal from the crucible, the crucible is actually raised above the axis of the rotation as it is rotated. Connected to the crucible and extending outwardly therefrom through the back portion of the furnace chamber in a direction substantially perpendicular to the lateral extent of the trunnions are a pair of flexible electrical leads 74 and 75. It has been customary to extend these leads outwardly in the direction of the trunnions, but the connection just described is considered an improvement over this former manner of electrlcal connection in that there is no chance of the leads being twisted as often happened with the former arrangement.

Referring now specifically to FIGS. 1, 5 and 6 the mechanism for rotating or tilting the crucible to pour the metal therefrom is shown. Extending through the wall 50 of the furnace chamber is a shaft 78. The shaft 78 is connected at one end of the chamber to trunnion 68 by means of a tongue and slot arrangement 79. The shaft 78 rides in a bearing 80 within the wall 50 of the chamber and has a pair of O-rings 81 and 82 which insure a good seal between the shaft and bearing at this point. Positioned bewteen the O-rings 81 and 82 is an annular groove 83 which is connected to an axially extending grease bore 84 which extends to the outermost end of the shaft and provides a conduit through which grease can be inserted between this point of rotation in the bearing 80. Extending outwardly from the furnace chamber wall and enclosing the portion of theshaft .at this outermost portion is a housing 85. Mounted within this housing and rotatably mounted to the shaft 7-8 by means of a key 87 is an annular collar 88. The collar 88 has a slot 90 formed therein. The slot 90 is positioned to receive a rod 91. This rod 91 has a handle 92 mounted on the uppermost end thereof and has a small laterally extending pin 93 mounted within the rod 91 and extending laterally therefrom. A compression spring 94 is mounted about the rod 91 and serves to urge the *rod 91 downward into the slot 90 when pin 93 is inserted within a slot 95 as shown in FIG. 5. By raising the rod 91 by means of the handle 92 so that the pin 93 is removed from slot 95 and rotated so that it cannot drop into the slot 95, the rod will be removed from the slot and rotation of the crucible can then be effected.

This rotation of the crucible is effected hydraulically in this embodiment by means of a lever 97 which is keyed to shaft 78 by key 87. One end of the lever 97 is mounted to a clevis 98 which is in turn connected to the plunger 99 of a hydraulic cylinder 100. The stroke of the hydraulic cylinder is sufiicient to radiate the shaft 78 and the crucible about 100 which will effect pouring of the molten metal from the crucible, and to about 90 for feed of an ingot into the crucible. An elongated lever handle 102 is mounted at the outermost end of shaft 78 to provide means for manually tilting the crucible and for positioning the crucible properly so that the rod 91 can be inserted into slot 90 to lock it in its upright position.

Referring now to FIGS. 1, 2, 3 and 4 apparatus is shown for loading the metal to 'be melted in the form of an ingot and positioning the mold into which the molten metal is to be cast within the furnace chamber 11. Both the feeding means for the metal charge and the mold positioning means are mounted to rotate about a common axis in the mold chamber from a position adjacent the outer door 17 to a position in the furnace chamber 11. As will also be seen both these means are rotatable around a common axis, but can be independently rotated to and from the respective chambers. Mounted vertically within the load chamber is a shaft 110. This shaft has a tapered bottom portion which is seated within a bronze rider 111 in the bottom portion of the chamber, and the upper end portion extends through the double-walled cover plate 12 within a bushing 113 which is mounted at the cover plate. It is to be noted that the double-walled cover plate consists of two plates which are spaced apart'and define a water jacket therebetween through which water is circulated as a coolant in a similar manner as that described in relation to the furnace chamber 11. Rotatably mounted adjacent the end portion of the shaft which extends out through the top closure 12 is a handle 114 which is mounted on shaft 115 and is rotatable within a bushing 116 .and has a small spur gear 117 fixed to the shaft. This small spur gear 117 meshes with a larger spur gear 118 which is fixed to the shaft 110. Thus by rotating the handle 114 this rotational movement will be transferred to the shaft 110 so that .anything fixed to the shaft 110 will similarly be rotated.

Fixed to the shaft 110 at the bottommost portion thereof is an elongated tubular member 120 which is keyed to the shaft by a key 121 so that it will rotate with the shaft 110. Fixed to this tubular member 120 by means of a vertical bracket 122 is a supporting platform 123. The supporting platform has an annular raised shoulder 124 thereon into which a mold 125 can be seated for positioning within the furnace chamber. This handle, gear, shaft and platform ararngement comprises the mold positioning means of the apparatus.

The ingot feeding means is positioned above the platform and is mounted on the shaft 110 but is not fixed to the shaft 110 to rotate with it. Instead, a shaft extends through the top closure 112 with a handle 131 positioned above the top closure and a spur gear 132 mounted within the chamber on the opposite end of the shaft 130. A bushing 133 is positioned at the top closure and the shaft is sealingly rotatable therein. The small spur gear 132 meshes with a larger spur gear 135 which is fixed to a tubular member 136 that is slidably mounted on the shaft 110. A collar grip 137 is fixed to the shaft at a point above the platform assembly and a thrust hearing 138 is mounted between the collar grip and the tubular member 136. By this arrangement rotation of the handle 131 will effect rotation of the tubular member 136 through the gearing arrangement and about the thrust bearing and collar support.

Fixed to the tubular member 136 and rotatable therewith is a first vertical bracket 140 which supports a platform 141 on which a hydraulic actuator 142 is mounted. A second vertical bracket 143 is also mounted on the tubular member 136 and extends therefrom to support a curved guide platform 144 on which an ingot scoop 145 is slidable upon actuation by the hydraulic actuator.

The hydraulic actuator 142 consists of hydraulically actuated rotary vane 146 which has a radial link 147 fixed to the rotary vane and is rotatable therewith. A linear arm link 148 is pivotally attached to one end of the radial link and has a pair of spaced parallel wheels 149 attached to the opposite end of the linear arm link. Also attached to the end of the arm link to which the wheels 149 are attached is an elongated scoop 158 into which an ingot is placed for carriage into the furnace chamber and for linear advancement into the crucible. The curved guide platform 144 on which the scoop 150 rides has a pair of radial bearings 152 extending Within the convex portion of the curved platform and the scoop rides against these radial bearings as it is linearly advanced. When the rotary vane 146 is rotated in a counterclockwise direction (relative to the view shown in FIG. 3), the radial link and arm links 147 and 148 cause the scoop to be linearly advanced in the curved platform 144 so that an ingot indicated as 154 in FIG. 3 can be inserted into the crucible when the ingot feed means and the crucible have been aligned.

Mounted at the forward end of the curved guide platform 144 is a rod 155 which is pivotally attached to the platform at its end portion 156. Extending inwardly from the rod 155 is an extension 157 which as shown in FIG. 3 rides along the outermost surface of an ingot as the ingot is linearly advanced into the crucible. Once the trailing end of the ingot passes the rod 155 in its insertion into the crucible the rod 155 will drop laterally across the curved platform into a slot 158 formed on the leading edge of the platform. When the rod 155 is in the slot I 158 and the scoop is subsequently withdrawn from the crucible the rod 155, substantially as shown and indicated in FIG. 4, it will rest across the trailing end of the ingot and will prevent withdrawal of the ingot with the scoop with the crucible. This means for linearly advancing an ingot in combination with the tubular member 136, spur gears 135 and 132, shaft 130 and handle 131 comprises the means for feeding the charge to the crucible and by rotating the handle 131 the platform carrying the ingot can be moved from a position adjacent the outer door 17 as shown in FIG. 1 to a position in alignment with the crucible 63 as shown in FIG. 3. Then by hydraulically actuating the actuator 146 through a pair of flexible hoses 160 and 161, which extend outwardly from the chamber to a four-way valve, the ingot can be inserted into the crucible.

It is to be noted that a radiation shield 163 is positioned beneath the hydraulic actuator to prevent the heat from the cast in the mold from interfering with the hydraulic system of the actuator.

Once the ingot is positioned in the crucible and the crucible is tilted upright to the melting positioning, it is sometimes desirable to make alloy additions to the crucible. The apparatus shown provides means for making alloy additions to the crucible during heating and without breaking the continuous vacuum in the furnace chamber. Extending through the top closure 55 of the furnace chamber at a point near the back end of the apparatus are a pair of sight tubes 178 and 171. These tubes are essentially identical in construction, and description of one will adequately sufiice for a description of the other. These sight tubes consist of first pipe member 173 which extends through the top closure 55 and opens into the furnace chamber. Mounted to the end of the first pipe member 173 above the closure 55 is a ball valve 174 and handle 175. A further extension of a pipe member 176 is mounted to the valve 174 and has a nut 177 mounted thereon. An O-ring 178 is mounted in the nut 177 at its endmost portion and a sight glass 180 is positioned on the O-ring 178. The sight glass is a cylindrical piece of Pyrex, and it is through this glass and through the sight tube assembly that one can see into the chamber. The sight glass is held against the O-ring by the difference between atmospheric pressure and the vacuum pressure within the chamber. Mounted directly below the sight tube assembly 170 and 171 are containers 182 and 183. These containers are fixed on right angle rods 184 and 185 and are connected to pivot on journals 186 and 187 which extend through the side wall of the furnace chamber and are surrounded at the chamber with bushings 188 and 189 as shown in FIG. 5. The manner in which the assembly is mounted in the side walls is shown in FIG. 7 connected to shaft 187 in which the bushing 189 surrounds the shaft 187 about a pair of spaced O-rings 190 and 191 on a shaft 187. Connected to the endmost portion of the shafts 187 and 186 along the portion thereof which extends out beyond the chamber are handles 192 and 193. In operation, alloy additions are made by removing the sight glass 180 after the valve has been closed, inserting the additions, and opening the valve so that the alloy additions can pass through the sight tube assembly and into the container 182. The container 182 is then rotated by its handle 192, shaft 186, and right angular rod 184 which are all positioned so that the container 182 will be pivoted in overlying relationship with the crucible so that the contents of the container will be emptied into the crucible by simply rotating the handle.

It is to be noted that at several positions at the top of both the load and furnace chambers sight glasses 195 are shown and these glasses are used to check on the operation proceeding within the closed chambers.

It is further to be noted in FIG. that a hydraulic bulkhead door control valve 196 is shown mounted on the side wall of the furnace and a hydraulic crucible pouroif control valve 197 is also mounted on the Wall; these valves are connected up with the respective bulkhead door and crucible assemblies in a conventional manner.

In preparing the apparatus for operation, the load chamber 10 can be physically separated from the furnace chamber 11 because the load chamber is mounted on wheels 44- for ease of movement toward and away from the furnace chamber. When the two chambers are physically separated, a worker can clean or adjust the apparatus contained in the furnace chamber 11 by reaching through the opening 22. When the apparatus is ready to be operated the load chamber is rolled into abutting contact with the side 23 of the furnace chamber and it is locked in that position by latches 46 and 47 as shown in FIGS. 1 and 5. The intermediate bulkhead door 25 is in its closed position and thus the furnace chamber is closed off from the load chamber.

With the apparatus in this position the vacuum exhausting system operative through the exhaust chamber 60 is activated and a high vacuum is created in the furnace chamber. While this furnace chamber is being brought to this high vacuum the outer door 17 leading into the load chamber is opened and a metal ingot 154 is inserted into the metal charge feed means onto the scoop 145 which is located adjacent the door as shown in FIG. 1. The door 17 is closed and the exhaust system which is operative through exhaust system 61 leading into the load chamber is actuated and a vacuum is thereby created in the load chamber. Once the vacuum in the load chamber equalizes the vacuum in the furnace chamber the bulkhead 25 is opened by activating the hydraulic cylinder 35. Then handle 131 is rotated causing this rotational movement to be transferred through gears 132 and 135 to the cylinder 136 so that the ingot 154 which is positioned on the scoop 145 will be fed from the load chamber into the furnace chamber. At the same time that the ingot feeding means is actuated hydraulic cylinder 100 is also actuated after releasing the stop rod 91 from the slot and the crucible 63 is correspondingly tilting substantially 90 so that it is positioned in perfect alignment with the scoop 145 of the ingot feeding means when the ingot is positioned in the furnace chamber. This alignment is shown in FIG. 3. The hydraulic actuator on the ingot feed means is then actuated by hydraulically feeding a fluid through one of the flexible hoses 160 and 161 so as to cause the rotary vane 146 to be rotated thereby advancing the linear arm link 48 in a direction toward the crucible 63 so that the scoop 145 with the ingot 154 thereon will be inserted within the crucible. The rod 155 drops into slot 158 so that as the scoop is retracted by actuating the rotary vane 146 to rotate in the opposite direction, the trailing end of the ingot will be prevented from being retracted with the scoop by means of the rod 155.

The handle 131 is then turned once again and the platform 144 is fully withdrawn into the load chamber in its position adjacent the door 17 as shown in FIG. 1. Hydrulic cylinder 35 is actuated once again and the intermediate door 25 is closed tight so as to sealingly close off the respective chambers. Hydraulic cylinder is actuated so as to withdraw plunger 99 and rotate the crucible 63 to its upright position shown in FIG. 6. The rod 91 can now be inserted within the slot 90 so as to hold the crucible in this upright position. The ingot is then melted in the crucible.

As soon as the intermediate door 25 was closed, the vacuum was released in the mold chamber, and once the vacuum is released, the outer door 17 can be opened and a new ingot can be positioned within the ingot feed ing means in the same way as ingot 65. Also a mold is positioned on the mold platform when the door 17 is opened. When the ingot and mold are so positioned, the door 17 is closed and the exhausting system is actuated through the exhaust chamber 61 so as to create a vacuum in the load chamber which is equal to the vacuum in the furnace chamber. By the time the load operation is completed and the vacuum has been equalized in the load; chamber, the ingot has been melted to molten metal. The bulkhead door 25 is once again opened by the hydraulic cylinder 35 and the mold 125 is positioned in the furnace chamber through the opening 22 by rotating handle 114 so that this rotation is transferred through the gears 117 and 118 to a shaft 110 and ultimately to the platform 123. When the mold on the platform 123 is properly positioned within the furnace chamber substantially as indi cated in FIG. 1 the rod 91 is then lifted from within the slot 90 and hydraulic cylinder 100 is actuated causing the crucible to rotate about l00 so as to pour the molten metal into the mold 125.

After the molten metal has been cast into the mold the ingot feed apparatus is put into operation by rotating.

handle 31 and once again causing the scoop with the new ingot to be aligned adjacent the opening in the tilted crucible 63. The hydraulic actuator of the ingot feed means is again actuated and the new ingot is fed into the crucible. v

131 and 114 respectively. When the mold platform and the ingot feed means are fully back into the load chambet adjacent the door 17, the hydraulic cylinder 35 is actuated and the bulkhead 1'25 is closed tight once again. Hydraulic cylinder 1% is actuated again and the crucible is brought into its upright or melting position. Simultaneously the vacuum in the load chamber is released, and once released, the door 17 i opened and the mold with the cast metal therein can be removed from the load chamber. When the door is opened a new mold and a new ingot are loaded onto the platform 123 and the scoop 145 respectively. Then the door 17 is closed tight again and the vacuum is created in the load chamber and the operation is repeated.

It was found that with the apparatus shown, in which a 100 kw. power supply was used for a 25 lb. melt, the complete cycle is approximately 6 minutes per mold.

An additional feature of the apparatus is that in prac tice a heated ingot is often placed into the crucible to maintain the crucible temperature in order to minimize thermal shock of the crucible. With this apparatus the ingot can be removed while hot and still under vacuum by means of the loading arm; this is impossible with equipment presently available.

We claim:

1. A method of casting molten metal under a vacuum comprising:

(a) loading a metal charge into a loading zone,

(b) creating a vacuum in said loading zone,

(c) opening the loading zone to a melting zone,

(d) continuously maintaining the melting zone under a vacuum,

(e) feeding the charge into the melting zone,

(f) heating the metal charge to molten metal in the melting zone,

(g) casting the molten metal in the melting zone,

(h) removing the cast in the mold from the melting zone into the loading zone,

(i) closing olT the loading and melting zone from each other, and

(j) removing the cast from the loading zone.

2. A method of casting molten metal under a vacuum comprising (a) loading a metal charge into a loading zone,

(b) creating a vacuum in said loading Zone,

(c) opening the loading zone to a melting zone,

(d) continuously maintaining the melting zone under a vacuum,

(e) feeding the charge into the melting zone,

(f) closing off the loading and melting zones from each other,

(g) loading a mold and a metal charge into the loading zone,

(h) heating the metal charge to molten metal in the melting zone,

(i) opening the loading zone to the melting zone,

(j) positioning the mold in the melting zone,

(k) casting the molten metal in. the melting zone,

(I) loading the metal charge into the melting zone,

(m) removing the cast in the mold from the melting zone into the loading zone,

(n) closing off the loading and melting zones from each other, and

(o) removing the cast from the loading zone.

3. A method according to claim 2 comprising adding alloy additions to the metal charge in the melting zone when the zones are close off from each other Without destroying the vacuum in the melting zone.

4. A method of casting molten metal under a vacuum comprising 1 (a) loading a metal charge into a loading zone,

(b) creating a vacuum in said loading zone,

(0) opening the loading zone to a melting zone,

(d) continuously maintaining the melting zone under vacuum pressure,

(e) feeding the charge into the melting zone,

(f) closing off the loading zone from the melting zone,

(g) heating the metal charge to molten metal under vacuum in the melting zone while it is closed off from the loading zone,

(h) releasing the vacuum in the loadin zone,

(i) loading a metal charge and a mold into the loading zone while the loading zone is closed off from the melting zone,

(j) creating a vacuum in the loading zone to equalize the vacuum in the melting zone,

(k) opening the loading zone to the melting zone,

(l) positioning the mold in the melting zone,

(m) casting the melt in the melting zone,

(n) feeding the metal charge into the melting zone,

(0) removing the cast in the mold from the melting zone into the loading zone,

(p) closing otf the loading and melting zones from each other,

(q) releasing the vacuum in the loading zone, and

(r) removing the cast from loading zone.

References Cited UNITED STATES PATENTS 2,713,183 7/1955 Winkler 164-258 2,788,270 4/1957 Nisbet et al.

2,825,945 3/1958 Ulrech et a1. 164-258 2,932,069 4/1960 Takahashi et a]. 164--256 2,983,973 5/1961 Parlanti 164-65 3,234,606 2/1966 Smith l64-50 X J. SPENCER OVERHOLSER, Primary Examiner R. SPENCER ANNEAR, Assistant Examiner 

